The Guggenheim Solar ETF (NYSEArca: TAN) still ranks as this year’s best non-leveraged exchange traded fund with gain of over 130%, but investors that recently started new positions in the fund probably are not smiling.

For all the attention TAN received on its way up, and that attention was ample, the ETF has somewhat quietly lost 8.7% in the past month. Now TAN faces a possible technical breakdown, the likes of which it has rarely flirted with as the fund has more than doubled this year. [Seduced by Solar ETFs]

“Until November 26, TAN had not made contact with its 50-day moving average since August 28.  These days, the 50-day moving average has become home.  Since November 26, TAN has not even been able to climb as high as its 20-day moving average, which is currently $39.40.  With the 20-day providing overhead resistance, TAN is now trapped in a range with $37.23 as support,” writes John Burke for Wall Street Sector Selector.

The daily chart shows TAN currently resides slightly below its 50-day simple moving average, a scenario that has occurred several times this year though one that usually has not last more than a few days. TAN is also 4% below its 20-day line.

Also weighing on TAN have been slack performances by some of the ETF’s marquee holdings. First Solar (NasdaqGM: FSLR) is down 3% in the past month. That stock is TAN’s largest holding with a weight of 7.31%. Elon Musk’s SolarCity (NasdaqGM: SCTY) has plunged 11.5% in the past month and that is with the benefit of a 5.3% gain Thursday. [SolarCity Could Boost Solar ETFs]

“Despite its 0.55 percent decline to $52.17 on Wednesday, SolarCity remains 6.33 percent above its 50-day moving average, after breaking above the neckline of the head-and-shoulders pattern on its chart during Friday’s shortened trading session,” according to Wall Street Sector Selector.

SolarCity is TAN’s fifth-largest holding with a weight of 5.5%.

First Solar “broke the neckline of the head-and-shoulders pattern on its own chart and finished the session 14.37 percent above its 50-day moving average,” Wall Street Sector Selector noted.

Guggenheim Solar ETF