Those lights won't be enough to flower the plants. In the short term, assuming they are LED, you may be able to squeeze more out of them by removing the diffusers, but it still won't be nearly enough.
The older plant is very small for 3 weeks due to lack of light. With better lamps they would be at least 2 or 3 times that size by now.
You'll also need a proper carbon filter and exhaust fan unless you're ok with a strong smell leaking from your grow area.
Growing on a budget can be done, but you'll find that if you really enjoy the process, you'll gradually end up spending the money for good equipment, as well as a lot of bad stuff if you keep trying to compromise, so seriously consider just going right for the good stuff. You'll probably only need a single, decent 100w LED board or strip for that space, so the investment isn't that big.