Hard to be certain as to what is happening but the following things come to mind:

1) double check your TAE. It may be a simple error by whoever measured out everything. Try to borrow some from another lab to test.

2) be sure the agarose is thoroughly molten before casting the gel

3) heat treat the ladder (10min at 65C).

Try washing your gel running equipment too (combs, casting tray, box, etc.). Rinse very well with distilled water.

Salt buildup on electrophoresis equipment can also cause this sort of messy/smeared bands.

Make sure the agarose is completely solidified before you remove the gel combs. Pulling them too early will cause "wobbly" wells and bands.

Good luck!

• Agarose Concentration: Test with different concentrations of agarose (e.g., 1.0%, 1.2%) to see if that improves separation.
• DNA Ladder Quality: Try a different batch or brand of DNA ladder to check if the ladder you're using is causing the merging issue.
• Gel Preparation Consistency: Ensure that the agarose is well-mixed, thoroughly melted, and poured evenly to avoid inconsistencies in the gel.
• Buffer pH: Double-check the pH of your 1x TAE buffer to ensure it’s within the correct range.
• Electrophoresis Chamber Temperature: Monitor the temperature during the run, as excessive heat could cause bands to merge.
• Voltage and Time Balance: Try running the gel for a slightly shorter time with the lowered voltage (55V) to avoid over-running, which can cause diffusion of bands.

Plausibly, Company A marker has a high concentration which leads to overloaded gels. In that case, 2- or 3-times titration would help to solve the issue with doubled bands.