what i think you mean by bleached color can mean too much light. do you use a moisture meter to tell you when to give them water? a more consistent temperature could help with germination (seedling heat mat with a thermostat).

Are you watering from the top or the bottom. Could you be watering too much?

I water every day, giving each seedling a desert-spoon of water. That's for 3" pots. When I used smaller pots or cell packs, I gave them just a teaspoon of water every day. This seems to work for me because otherwise I would over-water everything.

I water when the media is near-dry (pale and lightweight to the touch).

I alternate between top and bottom - top to flush excess salts, bottom to keep plants dry.

They dry out quickly, though.

What kind of pro mix did you use? HP drains too fast and is made for plants that don't like wet feet. BX retains the water better and is what I use for starting plants. All purpose has fertilizer and is not good for seedlings. My basement is much like yours in temp. and things grow well. I do have a mylar sheet draped over my lights to reflect the light and keep the plants a little warmer but then the lights are out at night.

I'd say if you are getting mold you are watering too much. At the first sign of mold sprinkle the soil with cinnamon and cut back on the watering. Cinnamon is a natural fungacide but it has to be used at the first sign of mold. Cuttings do better if put of a heating mat. I started 38 pelargonium cuttings and ended up with 32 plants. Fungus needs cool and wet to grow.

Some seeds like heating mats too but not all. Look at the germination temp. If it's 60 to 70 you'll kill the seed if put on a heating mat. My friend started her snapdragons on a heating mat and got not one plant. The higher temp. killed all the seed. However those that like higher temps. for germination benefit from the mat.

any chance of pictures?

You need constant airflow from a fan or slightly open window in the seedling room.

Sprinkling a layer of shredded sphagnum moss (I use No Damp Off) on top of soil after planting seeds, will help prevent mold growth.

Bottom water only and no heat mat after germination. I keep my plants at 65 degrees or less. Washing out salts isn't needed for seedlings that are in pots a short time before planting out. That's what we do for houseplants.

Try watering with a weak Chamomile tea. Also, putting a thin layer of sand at the top level is suppose to help because it dries out quickly. I haven't tried the later, but have had good success with the tea.