Can I switch from t5s to hps @ 3 weeks of flower?

*Have 6 ladies ready to flower but unfortunately I only have one 400 hps with 4 ladies on week 5 under it. So my question is can I put my 6 freshies in my flower room under 2 t5 bulbs (one blue one red) for the time being and in 3 weeks harvest my big ladies and slide the freshies over under the 400 hps. They will be in their 3rd week of flower by then?? Also will the lack of power under the 2 t5s make them suffer or lack in hormones and not flower them properly til week 3... I was hoping it wouldn't and actually benefit by maybe them not stretching so much seeing as I'm in a attic. But I don't Wanna lose total yield*in the long run. Could this happen??? Please shoot any answers my way thanks.*

I have kept plants vegging under small lights with no ill effect. Then put them under HPS to flower. They perked right up when they got some real light lol. ive never tried flowering under that small amount of light. I would think the plants would just take off when they got under the HPS.

definitely just wait. Use the extra veg time to top the plants a few more times. They will get bushier and wider.... which is always a good thing IMO.