It’s kind of fun to find this stuff out. A new 220 watt panel is now quite reasonable and that cheap controller is obviously inaccurate and could be replaced. Renogy makes a reasonably priced one and so does Grape Solar. A separate battery monitor would be a good idea too. I also changed out the WFCO for PD but I added lithium batteries. More power for fewer amp hr rating. Can be discharged 80% and the electronic monitor just turns them off if they get that low. Also turns off charging if it’s below 32° but they still release power. Insulating the battery compartment helps with this. We camped in the cold this spring and had no issues.
You will be glad you had issues because now you are more knowledgeable. I would have removed them for a deep charge too. You could even take them to an Auto Zone and they will do a deep charge and cell test for you. I was a terrible battery user for years. Now I don’t worry about it.