Transplant question

Hello growers! I transplanted clones from solo cup to a 5 gallon. I am beginner grower. Plants are 4-5 feet and 3 weeks Into flower. The bottom leaves keep going yellow. People have mentioned that I should transplant to 10-15 gallon. My question is do I stick it out with the 5 gallon this season and next year do it right? Or should I transplant 3 weeks into flower. When I look at the bottom of my planter I see roots. Thank you.

If they're in plastic I'd do it.
Fabric I'd leave them alone

Just leave them. Maybe you are low on nutrients. What’s the soil medium like? Depends if it’s thick or really airy.

Sounds like they are hungry, or the lowers are not getting enough light for the plant to justify their existsnce.

Watch out for that mustard water!