IMO, that plant is actually pretty healthy, with a couple issues.
What I see:
-You just transplanted so the rootbound condition that you probably had before judging by the downturned leaf edges and tips visible on some leaves is taken care of.
-Yellow leaves can be caused also by insufficient light, and you just upgraded.
-Time to start feeding... that's a hungry, nitrogen deficient plant. Since you are only in the first couple weeks of flower, you can feed a grow fert safely. You DO need a complete fertilizer with micros, and be certain that your soil runoff pH reads between 6.3 and 6.8. Give a 'grow' fert or your bloom fert plus a weak dose of fish emulsion until the end of week 2 of flowering to keep that yellow from spreading this early in the game.
You rventilation is correct.
You will need a much larger pot in about 3 weeks, as SOON as your roots have filled that one, so be prepared for that. One gallon per foot of main stem is the minimum.