I finish in 1 gallon pots, it can be tricky and I have to water every day or every other day in flower.
What works for me is using a well-amended, living soil, and for my current grow 1 part megacrop at lower strength regularly once the plants get mature enough. Some PK booster in flower too.
But the trick is not letting them get too dry, and not watering to run-off. I try to take advantage of the living soil as much as I can in a 1 gal pot, and living soil likes to maintain a certain moisture level. Any sufficiently aerated soil can work well with constant moisture. Just ask the SIP guys.
When you let living soil get too dry, the beneficial microbes die off or go dormant, and salts form during evaporation. Watering to run-off washes out lots of beneficial things in your soil. Doing both of those things regularly and your plants end up looking like yours did. And they looked underfed.
You still want to water until fully saturated, and it’s best to learn by feel/weight. A tiny bit of run off is fine.
And it’s Ok to let your pots get pretty light, especially in veg where we want those roots to spread out through the medium. But if the top of the soil turns rock hard dry, you’re waiting too long. In general you want to avoid pockets of dry or damp root balls. It’s a balance.