My advice if you truly want 'dull' and less light is to ask around and get 'old' tubes when others are replacing them. T8s typically run on magnetic ballasts and therefore deteriorate after a year or so compares to electric ballasts which tubes can last for 3+ years with only 5% loss. So some already deteriorating tubes from a 'mate' or LFS will cost next to nothing and you will be helping the environment
Alternatively buy some very very cheap tubes from the DIY store. The absolute budget ones will be a CRI of around 50% whereas most aquarium tubes are reasonably good in the 70/80% range. The budget tubes won't last as long in most casers but will be pretty yellowish like the one you have at the mo.
If you have a prefeerence for a 'dull' bulb then thats fine but if thinking a 'dull' bulb will alleviate the problem then it is more likely quite the reverse. The bulbs that look 'dull' to the human eye are more often than not providing more usable light.
As said above the Arcadia Tropical is very dark in appearance and gives the tank an almost pink appearance:
If that is the appearance you are after then get one
However being 4000K they are in the perfect plant range for those who believe in the K ratings being best for plants.
My advice if you truly want 'dull' and less light is to ask around and get 'old' tubes when others are replacing them. T8s typically run on magnetic ballasts and therefore deteriorate after a year or so compares to electric ballasts which tubes can last for 3+ years with only 5% loss.
Then if you do like a more natural light colouration (5500-7500K) then you can still achieve the colour without having so much light. It would look a little less bright too.
The 'K' ratings are more a human thing IMO and just give options for the 'tint' you give the tank. Many disagre and many will point to 'evidence' but many aquascapers can show otherwise.
p.s. the blue LEDs will not hurt anything.
As you don't have a planted tank there will be no problem in using a timer to switch the lights on for a couple of hours pre work and a few hours after work but try to reduce the total a little. between 8-10 is what planted tank users do and if anything it is more important in a non planted tank because there are no plants to 'counter' the algae.
IMPORTANT. With fluorescent tubes you MUST use an old style mechanical timer (the type with the dials on it and not a digital timer unless it clearly states it can be used with flourescent tubes (These can be qquite costly.)
As for the overfeeding you are in effect adding fertiliser for the algae. In a planted tank it wouldn't matter too much (within reason) but in a non planted tank it will.
Regards
AC