Help!!! My buds wont swell up...why???

I'm using foxfarms also and I noticed significant fatting in the 5th week of flower.
Looks great.

Heres an update. This is the ending of the 4th week. Looking a bit frostyer than the begining of the week and a little bigger. what do you guys think my final yield will be from these 4plants?

Damn, looking nice and frosty. I'd say at least 6oz as I had a white widow that i burnt to shit and it still gave me 3/4 of an oz dried and cured. All of your plants are looking much better than mine did so i would assume you should get at least double

Shoot for 1.5 to 2 oz per plant. That's probably on the low end.