Watson chewing Sherlocks hair off

Hi All - sorry for the huge block of text...I want to know if anyone has dealt with hair being chewed off?

As the title says I've been having this problem for 2 months or so ( I think it might be petering off but I worry that it might happen again).

Sherlock is a very chill for the most part and tolerates just about everything he's neutered and 1 year 7 months old now. Watson is a puppy and rambunctious...he's always been mouthy and loves to chew on things and just hit 9 months. To make this clear Watson chews on EVERYTHING - he's already cracked one of his teeth when the grandparents were dogsitting and had to have it extracted...

So my problem started out 2 months ago when Watson was about 7 months old and intact at the time. He started pulling the hair off his toys and actually coughed up a hair ball - so I then took away toys that he could pull hair from to prevent future choking hazards. Once I took them away by the next day he was chewing Sherlock's hair. I bought the bitter apple spray that next night when I realized it was being chewed off and not cut ( I thought maybe my roommate had cut some off at first). It did not deter Watson one bit. And Sherlock has never seriously corrected this behavior...which has led us to where we are now.

I've attached pictures to show the extent - the back area is actually worse now than the clear back pic shows. The other 3 are the most recent pictures and it creeps down the left side (for some reason all the hair on the right side is untouched).


I got him neutered so that I could take him to daycare ( I assumed boredom caused the chewing).
Here's the thing - I've never caught Watson chewing it off. We had assumed it was during play since they play a lot but again I couldn't be sure. I let the daycare know to watch out for this and to separate if needed. Upon pickup she said that Watson started chewing on Sherlock's hair while they were resting together during break time and Sherlock just laid there.

In all honesty I've seen Sherlock "Munching" on Watson's hair more often then I've seen Watson chewing on Sherlock's. The difference is that Watson is actually chewing it off. I have a large supply of toys out for them that is rotated, a couple of the longer yak chews, and a few hooves for them (when I'm watching) to try and keep him occupied.

Any suggestions? My next step would be to crate Watson but I don't know how to correct behavior when I've never seen it happen.

Background Info:
He has free reign of the apartment with Sherlock since he's potty trained and knows not to chew things he's not supposed to (except his brother apparently). For exercise: I used to take them on ~30-40 min walks in the morning, an afternoon bathroom break, and the dog park ~3 times a week plus evening walks (and a bit of training). We now have an apartment with a large dog park and start the day off there (20-40 mins) plus a short walk before I leave and a continuation of the afternoon break and evening schedule. I do drop them off at daycare once a week as well.

Watson has had surgery on his back right leg. His growth plate was completely fractured when I dropped him off for a meet and greet daycare visit on Rover when he was 5 months old (she was well reviewed but had larger dogs that I was not made aware of). It has healed completely and he was cleared for all activity 2+ months ago. The issue is that I think his knee gets sore when he has too much activity and he ends up limping along on that leg for a few hours or up till the next day. So I can't let him go completely ham chasing other dogs either without him potentially hurting/it being sore

 

Thanks for the reply guys! I will definitely keep separating them :| It sucks since I'm at work most of the day besides the lunch break, so I feel bad crating Watson for that long. Does it stop after a certain age? I'd hate to have to keep them separated for years!