I think the Copper Red DT females caudal fins are pretty even myself, it may be the camera angle. If you are wanting to continue with the Marble and DT genes you need to get a female with similar colors. The first two you have are Crowntail and if you breed them to your male that will get you an assortment of Halfsuns and Combtails, mostly Green with Red wash and no DT's unless they are a carrier of the DT gene. Personally I think $17 and $18 for a female is a bit much. I don't charge more than $9 or $10. I charge $10 for priority and $30 for express with no extra charge for the heat pack. By the time you pay for the express shipping and heatpack with an $18 fish you're looking at $56.50. Ouch! I just think that's a little steep. Here's an alternative.
I've been breeding DT's for the last 3 years and have only done one DT to DT spawn 3 months ago. The other 5 or 6 generations I breed DT to ST. Then ST to ST from that spawn to get a percentage of DT in the next generation.You shouldn't breed DT to DT for consecutive generations or you will get deformities in the fry. If you are interested in looking at an assortment of DT and Marble females just send me a PM.